Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a turbine interstage seal with balancing capability.
Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as a large frame heavy-duty industrial gas turbine (IGT) engine, a hot gas stream generated in a combustor is passed through a turbine to produce mechanical work. The turbine includes one or more rows or stages of stator vanes and rotor blades that react with the hot gas stream in a progressively decreasing temperature. The efficiency of the turbine—and therefore the engine—can be increased by passing a higher temperature gas stream into the turbine. However, the turbine inlet temperature is limited to the material properties of the turbine, especially the first stage vanes and blades, and an amount of cooling capability for these first stage airfoils.
In the turbine section, an interstage seal is used to provide for a seal between a rotating part and a static part of the turbine. A labyrinth seal is typically used between a rotor disk with rotor blades and a stator vane to prevent hot gas from the mainstream gas flow from entering a rim cavity where the high temperature gas can be exposed to the rotor disk. A labyrinth seal typically has a number of teeth that rotate about a static surface and can even rub against the surface during operation. Because a turbine in a gas turbine engine is exposed to a wide variation in temperatures, the spacing between the labyrinth teeth and the static surface can vary. During an engine transient—such as engine startup or shut down—the labyrinth seal gap can vary widely and thus create a large leakage path.